1. Technical Field
The present invention relates generally to an improved data processing system, and in particular to a method and apparatus to perform fabric management. More specifically, the present invention provides a method and apparatus for pausing a send queue such that fabric attributes and components may be modified without tearing down existing fabric connections.
2. Description of Related Art
In a System Area Network (SAN), the hardware provides a message passing mechanism which can be used for Input/Output devices (I/O) and interprocess communications between general computing nodes (IPC). Processes executing on devices access SAN message passing hardware by posting send/receive messages to send/receive work queues on a SAN channel adapter (CA). These processes also are referred to as “consumers”.
The send/receive work queues (WQ) are assigned to a consumer as a queue pair (QP). The messages can be sent over five different transport types: Reliable Connected (RC), Reliable datagram (RD), Unreliable Connected (UC), Unreliable Datagram (UD), and Raw Datagram (RawD). Consumers retrieve the results of these messages from a completion queue (CQ) through SAN send and receive work completion (WC) queues. The source channel adapter takes care of segmenting outbound messages and sending them to the destination. The destination channel adapter takes care of reassembling inbound messages and placing them in the memory space designated by the destination's consumer.
Two channel adapter types are present in nodes of the SAN fabric, a host channel adapter (HCA) and a target channel adapter (TCA). The host channel adapter is used by general purpose computing nodes to access the SAN fabric. Consumers use SAN verbs to access host channel adapter functions. The software that interprets verbs and directly accesses the channel adapter is known as the channel interface (CI).
Target channel adapters (TCA) are used by nodes that are the subject of messages sent from host channel adapters. The target channel adapters serve a similar function as that of the host channel adapters in providing the target node an access point to the SAN fabric.
SAN fabric components, e.g., switches, routers and channel adapters, have several attributes assigned to them by a subnet manager. These attributes are accessible from a subnet administrator. The subnet manager is responsible for discovering, initializing, configuring and maintaining SAN fabric components. The subnet administrator is used to update and query some of the attributes assigned to the SAN fabric components. However, some of the attributes can only be assigned by the subnet manager during fabric initialization. Thus, in order to change these attributes, established connections in the SAN fabric must be torn down, the attributes changed, and the connections rebuilt in view of the changed attributes. It would therefore, be beneficial to have a method and apparatus for modifying SAN fabric components and component attributes without having to tear down existing connections.